192 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



solution. It also should contain a considerable amount of carbon 

 dioxide, to which the flavor of water is due. The dispersion of these 

 gases by boiling gives to -water a flat and disagreeable taste. The 

 inorganic salts held in solution in natural waters may vary within very 

 wide limits, both as to their nature and quantity ; ordinary drinkable 

 water contains about twenty-five to one hundred centigrammes of solid 

 residue per liter. Of this, carbonates, sulphates, alkalies, chlorides, 

 and earthy matters are the most constant constituents, although various 

 other substances, such as sulphur, iron, and lime, are contained in 

 waters of different localities, forming the so-called mineral-spring waters, 

 whose composition is subject to the very greatest variation. 



2. Nutritive Salts. — Of the salts which are essential for the nutri- 

 tion of animals the most important is sodium chloride. This substance 

 enters largely into the composition of all animal tissues and fluids, and 

 when not supplied in proper amount produces great disturbances of nutri- 

 tion, and a morbid craving for it has often been noticed. The effects of 

 the deprivation of salts, or the so-called salt hunger, will be alluded to 

 under the subject of Nutrition. Even the administration of an extra 

 ration of salt is sometimes of advantage; thus, the experiment has been 

 made of feeding two bullocks on food which in one case contained a 

 daily ration of five hundred grains of salt, while no salt was supplied to 

 the other. For five months no very evident results appeared ; but changes 

 then commenced which were very marked, even to the unpractieed eye. 

 In the bullock to which the salt had been supplied the hair was smooth 

 and glistening, and in the other rough and tarnished. This distribution 

 of salt in the diet was continued for a year, when the animal which had 

 been kept without salt had a rough and tangled hide, with patches where 

 the skin was entirely bare, while the other, to whom five hundred grains 

 of salt had been supplied daily, had all the appearance of a healthy, stall- 

 fed animal, was much more vivacious, and would have brought a much 

 higher price in the market. 



In addition to sodium chloride, phosphates, carbo-hydrates, and sul- 

 phates are also of great nutritive value, and are required for the main- 

 tenance of a proper nutritive condition of the animal! Carnivorous 

 animals receive a proper supply of phosphates in the animal foods, 

 especially in bones, whereas the herbivora derive them from the grasses 

 on which they feed. Phosphatic manures owe their value largely to the 

 contribution of phosphates which they make to the soil, and hence to 

 the grasses grown on them. The lime salts, as has been already indi- 

 cated, are essential for the development of the solidity of bones, and 

 when reduced in amount lead to various deformities of the bony 

 skeleton. Even suckling animals receive in the milk of their mothers 

 when normal a sufficiency of these inorganic matters ; thus, a suckling 



